This issue seems to be fixed now.

People reported it in the Microsoft Forums. That's all I know. Does MS read these posts? Probably not. I suspected that there are sufficient MS clients who use UDP in Hyper-V guest machines so that they'll do something about this quickly.

Yes with VMware or VirtualBox this does work. This is a ...

KB5017308 still has this issue.

Just a little Update: KB5016616 is also affected by the issue.

Hello Sparkbugz,
Happy to hear that it resolved the issue for you too. Now we just have to hope that MS fixes the issue quickly.

Hello FuryoftheStars,
Thanks for the hint!

Thank you very much Hornwitser! You pointed me into the right direction.
I am hosting the game on a Hyper-V server and KB5015807 must have broken something in the network stack. After uninstalling the update everything works again! Reinstalling it reintroduces the issue. Can I mark the this topic as ...

Hello Hornwitser,

So I did what you asked but there seems not to be a lot more info in the logs.

Hello Hornwitser,
Thank you for your answer but I don't think that this applies to my case. I have this issue no matter if the game is modded or not.
Attached to my comment you find the configuration and logs for a freshly installed server without mods and with a fresh save game.

Hello,
I have a headless server running on a machine in my network. This setup was running =~ one year now.
Between 2022/07/15 and 2022/07/22 something must have happened so that my setup is not working any more.

What did I do:
* 2022/07/15: Playing on said server with some friends
* 2022/07/22 ...